The present invention relates to a connector plug which is used for interconnecting audio-equipments, video-equipments, computers, and their peripheral equipments.
A typical prior art example of this kind of connector plug is disclosed in U.S. Pat. No. 4,684,199.
FIG. 1 shows the structure of this conventional connector plug, which is identified generally by 100. The connector plug 100 comprises a cylindrical metal cover 101, which accommodates a disc-shaped insulating body 102 fitted thereinto. A plurality of contact pins 103a to 103e are planted on the insulating body 102 in a manner to extend therethrough in the axial direction of the cylindrical metal cover 101.
The rear portion of the cylindrical metal cover 101 is fitted with an insulating cap 104. The insulating cap 104 is formed of a flexible insulating resinous material and has a rear cable lead-out portion 105 which has a number of slits and hence is elastic.
The exposed front portion of the cylindrical metal cover 101 has three protrusions or ridges 106, 107a and 107b which protrude radially inwardly from the inner cylindrical surface of the metal cover 101. The ridge 106 serves as a main positioning ridge and the other ridges 107a and 107b as auxiliary positioning ridges.
The cylindrical metal cover 101 has a cut-away part 108 open at its front end, extending between the auxiliary positioning ridges 107a and 107b. The cut-away part 108 is provided for avoiding abutment of the metal cover 101 against an internal part of the mating connector socket 200 shown in FIG. 2 and permits miniaturization of the socket. The connector socket is disclosed in, for example, U.S. Pat. No. 4,637,669.
The insulating body 102 has an insulating bar-like member 109 formed integrally therewith and extending forwardly from the front end face thereof together with the contact pins 103a and 103e. The insulating bar-like member 109 is provided at a different position according to the number of contact pins which are planted on the insulating body 102. The mating connector socket has a squarely-sectioned guide hole 201 for receiving the insulating bar-like member 109, and this ensures insertion of the connector plug into a mating socket of desired contact pin member.
The insulating bar-like member 109 is formed so that it extends slightly forwardly of the contact pins 103a to 103e but rearwardly of the front ends of the ridges 106, 107a and 107b. The connector plug 100 is inserted into the connector socket 200 in the following way. At first, the front circumferential edge of the cylindrical metal cover 101 of the connector plug 100 is inserted into an annular gap defined by an insulating body 204 and a cylindrical metal cover 206 of the connector socket 200 therebetween and then the connector plug 100 is turned, bringing the main positioning ridge 106 and the auxiliary positioning ridges 107a and 107b into engagement with grooves 202, 203a and 203b formed in the connector socket 200. In this instance, when the connector plug 100 is being turned about its axis for positioning, the tip of the insulating bar-like member 109 does not abut the front end face of the insulating body 204. It is only when the ridges 106, 107a and 107b have been brought into alignment with the grooves 202, 203a and 203b of the connector socket 200 by turning the connector plug 100 that the insulating bar-like member 109 can be inserted into the guide hole 201, and accordingly the contact pins 103a to 103e can be inserted into corresponding contact receiving holes 205a to 205e in the socket 200.
The prior art connector plug has its feature in that the main positioning ridge 106 and the auxiliary positioning ridges 107a and 107b engage the grooves 202, 203a and 203b formed in the peripheral surface of the insulating body 204 of the connector socket 200, defining the position where to insert the connector plug 100 into the socket 200.
The connector plug 100 is turned with the main positioning ridge 106 and the auxiliary positioning ridges 107a and 107b held in sliding contact with the marginal portion of the front end face of the insulating body 204 of the connector socket 200 until the plug inserting position is found. Accordingly, the front ends of the protrusions 106, 107a and 107b support the plug 100 at three points, enabling the plug 100 to be turned with its axis aligned with that of the socket 200.
In the connector socket 200 shown in FIG. 2, the insulating body 204 has an annular groove 207 formed in its front end face circumferentially thereof, and a cylindrical metal cover 206 is installed in the annular groove 207. The cylindrical metal cover 206 is formed by pressing a resilient metal sheet into a cylindrical form so that the opposing side edges are adjacent but spaced a certain distance apart, defining a slit 206A axially of the cover 206. The cylindrical metal cover 206 of such a configuration is disposed in the annular groove 207 with the slit 206A in agreement with the main positioning groove 207. The cylindrical metal cover 206 thus installed in the annular groove 207 is resiliently deformable radially thereof, and hence firmly grips the outer peripheral surface of the cylindrical metal cover 101 of the connector plug 100 inserted in the connector socket 200. Accordingly, the connector socket 200, though small in size, has a strong plug engaging force.
While in the above reference has been made to the connector plug with five contact pins and the mating connector socket, examples of connector plugs having different number of contact pins and a connector plug without the insulating bar-like member 109 are set forth in the afore-mentioned U.S. Pat. No. 4,684,199; accordingly, no description will be given of such prior art connector plugs.
Any of such conventional connector plugs is positioned, relative to the main positioning groove 202 and the auxiliary positioning grooves 203a and 203b of the connector socket 200, by turning the connector plug with its three protrusions 106, 107a and 107b held in sliding contact with the front end face of the insulating body 204 of the connector socket 200. In this positioning, the center axis of the connector plug can be held substantially in its correct direction because the plug is turned with the front marginal portion of the cylindrical metal cover 101 held in shallow engagement with the cylindrical metal cover 207 of the connector socket 200. However, there is a case where the front ends of the three protrusions 106, 107a and 107b do not accurately coincide one another in position within a predetermined tolerance owing to distribution in size. Furthermore, even if the three protrusions are formed accurately at predetermined positions, the connector plug may sometimes be held with its center axis slightly aslant. In these cases, the three protrusions do not simultaneously contact the marginal portion of the front end face of the insulating body 204 of the connector socket 200. In other words, only two or one of the three protrusions makes sliding contact with the front end face of the insulating body 204. As a result of this, the pressure of contact between the two or one protrusion and the insulating body 204 is greater than in the case where all the three protrusions are held in contact with the latter, and there is a tendency that during the rotational positioning of the plug the protrusion contacting the front end face of the insulating body 204 scratches its marginal portion and front edges of the grooves 202, 203a and 203b due to friction, scraping a resin powder off the insulating body 204. This introduces the possibility that the resin powder enters into the female contact receiving holes 205a to 205e of the connector socket 200, resulting in bad contact between the contact pins of the plug and female contacts of the socket.